Just how long does it take to cool a reactor?

[TimberWolf]

You're a project manager aren't you?

Fukushima I Nuclear Power Plant - Wikipedia, the free encyclopedia

Fukushima I – 1 460 MW
Fukushima I – 2 784 MW
Fukushima I – 3 784 MW
Fukushima I – 4 784 MW
Fukushima I – 5 784 MW
Fukushima I – 6 1100 MW

10% of 1GW (units 1 and 2) is 100MW. Allowing for inefficiencies in the power generation process that's probably 200MW of heat output that needs shifting.

A quick calculation based on specific heat capacity and latent heat of vaporisation of water, 1L @ 10 degrees C will require about 2650 kJ to boil, we have 200,000 kJ / s to get rid of, so we need about 80L of water a second to replenish the stuff that is turning to steam.

If you wish to avoid it turning to steam you have a much bigger problem, as most of the energy (2270 kJ) is absorbed by the vaporisation rather than the raising of temperature.

That's perhaps the cooling needed when things are operating normally, but what about when fuel rods are in an uncertain state (possibly melted), the control rods integrity questionable, plus the presence of water acting as moderator? A reactor working at 100% in a puddle on the floor?

[VectraMan]

The greatest radio-iodine releases ever seen so far occurred during US nuclear weapons tests in Nevada prior to 1970: Americans suffered the iodine equivalent of three Chernobyls during that period, but because they were not told about the hazard they didn't notice it. The bulk of the health effects came from children being fed contaminated milk, children being especially prone to thyroid damage from iodine; in fact they are the main group likely to suffer major effects. Millions of children were also fed contaminated milk following Chernobyl: according to the IAEA the incidence of thyroid cancer among such children and young people rose to one case in 4,500.

[TimberWolf]

If only they had built it a couple of miles underground, as I've been suggesting for years.

One of these days it won't just be earthquakes and tsunamis but bombs being used against nuclear power stations, and a fat lot of use a 20 foot wall will be then, or blow out walls, or even three foot thick containment vesssels.

And when the power station came to the end of its life, you wouldn't even need to dismantle it at vast expense, just seal off that branch of the tunnel and start a new power station in a parallel tunnel.

AtW mentioned this proposal a day or so ago and I asked him how you'd keep the reactor cool, with something like 2GW of heat to remove. Okay, getting water down there won't be a problem under gravity feed, but you might need to be pumping a tonne or more water a second (I did a rough calculation once but have forgotten the result) 2 miles uphill. Assuming you can't cool the water underground.

[doodab]

That's perhaps the cooling needed when things are operating normally, but what about when fuel rods are in an uncertain state (possibly melted), the control rods integrity questionable, plus the presence of water acting as moderator? A reactor working at 100% in a puddle on the floor?

Yeah, It's probably not even a ballpark figure. I've assumed some sort of thermal equilibrium while removing the heat generated after a normal shutdown. I also haven't allowed for any inefficiency in the cooling process, or for steam to be heated above 100 degrees once it's boiled.

I guess if the fuel rods are super hot, you need to work out how much extra cooling capacity is required to bring them back down to the target temperature.

[Churchill]

Build a sarcophagus around the damaged reactor.

We just need some very brave souls to go and build it.

Those chaps at Chernobyl were incredibly brave in their self sacrifice.

[TimberWolf]

Yeah, It's probably not even a ballpark figure. I've assumed some sort of thermal equilibrium while removing the heat generated after a normal shutdown. I also haven't allowed for any inefficiency in the cooling process, or for steam to be heated above 100 degrees once it's boiled.

I guess if the fuel rods are super hot, you need to work out how much extra cooling capacity is required to bring them back down to the target temperature.

You feel the fuel and control rods are still in place more or less intact?

[doodab]

AtW mentioned this proposal a day or so ago and I asked him how you'd keep the reactor cool, with something like 2GW of heat to remove. Okay, getting water down there won't be a problem under gravity feed, but you might need to be pumping a tonne or more water a second (I did a rough calculation once but have forgotten the result) 2 miles uphill. Assuming you can't cool the water underground.

The primary loop uses sodium I believe, and hfss no reason for coolant to travel to.and from the surface. The secondary probably allows the hot water to rise as steam, so should get back up there all by itself.

[TimberWolf]

The primary loop uses sodium I believe, and hfss no reason for coolant to travel to.and from the surface. The secondary probably allows the hot water to rise as steam, so should get back up there all by itself.

That's true, maybe the idea has merit. Thermodynamic efficiency might take a bit of hit though.

[MarillionFan]

AtW mentioned this proposal a day or so ago and I asked him how you'd keep the reactor cool, with something like 2GW of heat to remove. Okay, getting water down there won't be a problem under gravity feed, but you might need to be pumping a tonne or more water a second (I did a rough calculation once but have forgotten the result) 2 miles uphill. Assuming you can't cool the water underground.

Come on. All we need to do is find the team who've been working on making the London Underground cool in the summer.

Send them over to sort it out. Then push the useless ****ers in.

[TimberWolf]

So what about the spent fuel rods (there are an awful lot of them, far more than in all the reactors I hear). How much cooling do they need?